An electromagnetic flow meter includes a detector having a measurement tube, a magnetic excitation coil that generates a magnetic field orthogonal to a flow direction in the measurement tube, and a pair of detecting electrodes, disposed in the measurement tube, that face each other in a direction orthogonal to the flow direction of a fluid and the direction of the magnetic field. The electromagnetic flow meter supplies magnetic excitation current to the magnetic excitation coil and measures the flow rate of the fluid flowing through the measurement tube based on an electromotive force generated between the detecting electrodes when the fluid flows through the magnetic field generated by the magnetic excitation coil.
A rectangular waveform magnetic excitation system that switches the orientation of magnetic excitation current flowing through the magnetic excitation coil is used as one magnetic excitation system for an electromagnetic flow meter. In recent years, there are known techniques (PTL 1 and PTL 2) that reduce power consumption or known techniques (PTL 3 and PTL 4) that determine an abnormality such as emptiness of a measurement tube by adopting a so-called ternary magnetic excitation system that has a non-magnetic excitation period between a positive magnetic excitation period and a negative magnetic excitation period. In addition, there is another known technique that corrects error at the zero point of an output without setting the flow rate of a measurement target fluid to 0 (PTL 5).